A known method for manufacture of e.g. meat patties involves the use of an installation having a frame and a mould drum with an outer circumferential drum surface and a longitudinal drum rotation axis, often a horizontal axis. The drum is rotatably supported by the frame to revolve about the drum rotation axis. The drum has in the drum surface multiple mould cavities, each having a fill opening for the introduction of foodstuff mass, e.g. ground beef mass, into the mould cavity. A mould drum drive is coupled to the drum to drive the drum in a rotation direction. A mass feed member is stationary arranged at a fill position relative to the drum surface. This mass feed member has a single chamber with an inlet for the foodstuff mass to introduce foodstuff mass into the chamber and with a mouth facing the drum surface that is provided with the mould cavities. The mass feed member is adapted to transfer mass from the chamber into the passing mould cavities of the rotating mould drum when the filling opening of a mould cavity is in communication with the mouth at said fill position. The mass that has been filled into a mould cavity remains in said cavity for a while, commonly the installation has a closure member that extends in downstream direction from the mass feed member at the fill position and temporarily keeps the filled mould cavities closed downstream of the fill position, e.g. to allow the mass to become a more coherent food product. The mass in the mould cavity forms the food product, e.g. the meat patty. The installation comprises a pump that is connected to the inlet of the mass feed member and is adapted to feed foodstuff mass under pressure into the chamber of the mass feed member. A food products release or removal mechanism is provided, e.g. associated with the mould drum, and is adapted to cause or facilitate removal of the food product at a product removal position that is downstream of the fill position. It is for example known to provide air channels in the drum that extend to the cavities and allow to selectively introduce air that has been supplied from a manifold at a head end of the drum via said channels to between the drum and the product in order to facilitate the release thereof from the mould cavity. Other release or removal mechanisms, e.g. using a mechanical ejector, are also known in the art.
The production of moulded food products, e.g. meat patties, with such installations generally includes:                driving the drum in its rotation direction in a continuous, non-interrupted manner;        operating the pump so as to feed foodstuff mass to the mass feed member and establish a foodstuff mass pressure in the chamber of said mass feed member,        transfer of pressurized foodstuff mass via the mouth into each passing mould cavity,        release of the moulded products from the mould cavities.        
Some small capacity prior art moulding devices of the design mentioned above have a drum of minimal axial length that is only provided with a single circumferential array of mould cavities that are arranged at different circumferential positions on the drum surface. An example thereof is shown in U.S. Pat. No. 3,137,029.
It is also known to increase the capacity by lengthening the drum so that the drum has multiple of such groups in axial direction of the drum, or in general to have the mould cavities arranged in the drum surface in a mould cavities pattern with cavities at multiple, e.g. two, or four or more, longitudinal positions when seen in longitudinal direction of the drum and at multiple circumferential positions when seen in circumferential position of the drum.
It is common in prior art mould drums for these installations to arrange the mould cavities in straight or rectilinear rows of multiple mould cavities, said rows being parallel to the drum axis with the rows being offset from one another in circumferential direction. It is also common in such prior art mould drums that all mould cavities are of identical dimensions, e.g. circular contoured cavities, although other embodiments with non-identical cavities are known as well. Examples of known high capacity food product moulding installations and methods are found in e.g. WO 0030458 and WO2004002229.
In general drum type moulding installations allow for a high production capacity compared to well known slide-plate moulding devices, wherein a cyclically driven mould plate with a row of mould cavities is cycled back and forth between a fill position and a release position. At the fill position the row of mould cavities in the reciprocating plate is filled with foodstuff mass. It is common for these plate type devices to fill the mould cavities with foodstuff mass, e.g. ground meat mass, at a high fill pressure, said fill pressure being significantly relieved by suitable operation of the pump in the period when the plate starts to move away from the fill position. This is for example illustrated in U.S. Pat. No. 4,356,595.
In WO 2011005099 the issue of non-uniformity of the finally obtained food products is addressed, e.g. with regard to their appearance and shape. For instance in practical use of a high capacity drum mould device it is observed that in a batch of circular meat patties that are made of ground meat there are visible deviations from the circular contour of the mould cavities. These shape deviations are also non consistent within the batch. In WO 2011005099 it is amongst others proposed to embody each mould cavity with walls so as to define a plurality of moulding cells within each mould cavity in order to alleviate this problem.